Biomedical energization elements with polymer electrolytes

ABSTRACT

Designs, strategies and methods to form energization elements comprising polymer electrolytes are described. In some examples, the biocompatible energization elements may be used in a biomedical device. In some further examples, the biocompatible energization elements may be used in a contact lens.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation-in-part of U.S. patentapplication Ser. No. 14/827,589 filed Aug. 17, 2015 which claims thebenefit of U.S. Provisional Application No. 62/040,178 filed Aug. 21,2014.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Designs and methods to improve performance and biocompatibility aspectsof batteries are described. In some examples, electrolytes are providedin a solid polymer form.

2. Description of the Related Art

Recently, the number of medical devices and their functionality hasbegun to rapidly develop. These medical devices may include, forexample, implantable pacemakers, electronic pills for monitoring and/ortesting a biological function, surgical devices with active components,contact lenses, infusion pumps, and neurostimulators. Addedfunctionality and an increase in performance to many of theaforementioned medical devices have been theorized and developed.However, to achieve the theorized added functionality, many of thesedevices now require self-contained energization means that arecompatible with the size and shape requirements of these devices, aswell as the energy requirements of the new energized components.

Some medical devices may include electrical components such assemiconductor devices that perform a variety of functions and may beincorporated into many biocompatible and/or implantable devices.However, such semiconductor components require energy and thusenergization elements should preferably also be included in suchbiocompatible devices. The topology and relatively small size of thebiocompatible devices may create challenging environments for thedefinition of various functionalities. In many examples, it may beimportant to provide safe, reliable, compact and cost-effective means toenergize the semiconductor components within the biocompatible devices.Therefore, a need exists for biocompatible energization elements formedfor implantation within or upon biocompatible devices where thestructure of the millimeter- or smaller-sized energization elementsprovides enhanced function for the energization element whilemaintaining biocompatibility.

One such energization element used to power a device may be a battery.When using a battery in biomedical type applications, it may beimportant that the battery structure and design inherently provideresistance to incursions and excursions of materials. A polymerelectrolyte battery design may afford such resistance. Therefore a needexists for novel examples of polymer electrolyte batteries that arebiocompatible for use as biocompatible energization elements.

SUMMARY OF THE INVENTION

Accordingly, polymer electrolyte battery designs and related strategiesand designs for use in biocompatible energization elements have beendisclosed.

One general aspect includes a biomedical device which includes anelectroactive component and a battery. The battery may include a polymerelectrolyte, where the polymer electrolyte includes an ionic species.The battery also includes a manganese dioxide cathode. The biomedicaldevice also includes a first encapsulating layer, where the firstencapsulating layer encapsulates at least the electroactive componentand the battery.

Implementations may include one or more of the following features. Thebiomedical device where the battery further includes: an anode currentcollector; a cathode current collector; and an anode; where the anodeincludes zinc, and where the anode and the anode current collector are asingle layer. The biomedical device may also include a polymerelectrolyte, where the electrolyte includes poly (vinylidene fluoride).In some examples, the polymer electrolyte includes zinc ion. In someexamples, the battery may include manganese dioxide, and in someexamples, the manganese dioxide cathode includes jet milled electrolyticmanganese dioxide. The battery may be formed from a cathode slurry madefrom the manganese dioxide with polymeric binders and fillers such aspoly(vinylidene fluoride) and carbon black. The battery may have ananode formed from zinc, where the zinc may be in a foil form in someexamples. The battery may include a seal in encapsulating films thatenclose more than 90 percent of the battery portions not used for makingexternal contacts. When formed with these layers, a laminated structuremay be formed with hermetically sealed encapsulating such that thicknessof the battery is less than 1 mm. In some examples, the battery is lessthan 500 microns thick. The battery in some further examples may have athickness less than 250 microns.

Batteries may be formed in sheets and individual batteries may be cutout or singulated from the sheets. In some examples, the shape of thecut out batteries may be curvilinear

One general aspect includes a method for forming a battery whichinvolves obtaining a cathode collector film, where the cathode contactfilm includes titanium. The method also includes coating the cathodecollector film with a carbon coating. The method also includesdepositing a manganese dioxide slurry upon the carbon coating. Themethod also includes drying the manganese dioxide deposit. The methodalso includes depositing a polymer electrolyte including ionicconstituents onto the manganese dioxide deposit. The electrolyte may belaminated to the manganese deposit. The method also includes drying thepolymer electrolyte. The method also includes laminating a zinc foil tothe polymer electrolyte, such that the zinc foil may be an anode and ananode collector. The method also includes encapsulating the zinc foil,polymer electrolyte, manganese dioxide deposit, and the cathodecollector in a biocompatible encapsulating film. The method of alsoincludes the method further including singulating a battery element. Insome examples the anode current collector and the cathode currentcollect may be attached to an electroactive device of a biomedicaldevice. The battery and the connected electroactive device may beencapsulated in a second biocompatible encapsulating layer as a part offorming the biomedical device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIGS. 1A-1D illustrate exemplary aspects of biocompatible energizationelements in concert with the exemplary application of contact lenses.

FIG. 2 illustrates an exemplary battery cell with a polymer electrolyte.

FIG. 3A illustrates a first stand-alone, packaged biocompatibleenergization element with exemplary anode and cathode connections.

FIG. 3B illustrates a second stand-alone, packaged biocompatibleenergization element with exemplary anode and cathode connections.

FIGS. 4A-4F illustrate exemplary method steps for the formation ofbiocompatible energization elements for biomedical devices.

FIGS. 5A-5D illustrate exemplary battery characteristics for samplesmade with a polymer electrolyte according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods of forming and using biocompatible batteries with polymerprimary battery chemistry are disclosed in this application. The polymerelectrolyte is a key component that creates a battery with improvedability to contain battery chemistry within encapsulation and to lowerthe forces upon internal battery components contained within packagingor encapsulation. In the following sections, detailed descriptions ofvarious examples are described. The descriptions of examples areexemplary embodiments only, and various modifications and alterationsmay be apparent to those skilled in the art. Therefore, the examples donot limit the scope of this application. The anode formulations, and thestructures that they are formed into, may be designed for use inbiocompatible batteries. In some examples, these biocompatible batteriesmay be designed for use in, or proximate to, the body of a livingorganism.

An important need for the performance of biocompatible batteries relatesto the sensitivity of these batteries to their environment, and inparticular to the moisture in their environment. Batteries that haveaqueous electrolyte formulations may be significantly sensitive in theseways. In some cases, if encapsulation strategies do not prevent movementof water, water may move out of the battery into its surroundingenvironment, and this may result in the electrolyte drying up withsignificant impact to battery performance parameters such as internalresistance. In some other cases, water may diffuse into batteries ifencapsulation strategies allow water to cross them, even in smallquantities. The result of water diffusing into these batteries mayresult in diluting the electrolyte with an impact on battery performanceand in swelling of the battery body which may result in rupture of thebattery encapsulation with potentially significant impacts. Methods toformulate polymeric battery electrolytes may result in batteries thatare relatively insensitive to ingress or egress of materials such asmoisture. Such improvements may improve performance and/or decreaserequirements on sealing and encapsulating processes.

A battery with a polymer electrolyte which results in batteries that arerelatively insensitive to their environment may have numerous benefitsabove and beyond the basic need for such an insensitive battery. Forexample, such a polymer electrolyte may have significantly improvedbiocompatibility since the electrolyte cannot leak out as easily. Aswell, the resulting electrolyte and in some examples the separator thatit forms may be more resilient to downstream processing steps which maybe necessary in the processing of a biomedical device, for example, hightemperature and low vacuum necessary for overmolding. There may benumerous manners to form polymer based electrolytes with theseproperties.

Glossary

In the description and claims below, various terms may be used for whichthe following definitions will apply:

“Anode” as used herein refers to an electrode through which electriccurrent flows into a polarized electrical device. The direction ofelectric current is typically opposite to the direction of electronflow. In other words, the electrons flow from the anode into, forexample, an electrical circuit.

“Binder” as used herein refers to a polymer that is capable ofexhibiting elastic responses to mechanical deformations and that ischemically compatible with other energization element components. Forexample, binders may include electroactive materials, electrolytes,polymers, etc.

“Biocompatible” as used herein refers to a material or device thatperforms with an appropriate host response in a specific application.For example, a biocompatible device does not have toxic or injuriouseffects on biological systems.

“Cathode” as used herein refers to an electrode through which electriccurrent flows out of a polarized electrical device. The direction ofelectric current is typically opposite to the direction of electronflow. Therefore, the electrons flow into the cathode of the polarizedelectrical device, and out of, for example, the connected electricalcircuit.

“Coating” as used herein refers to a deposit of material in thin forms.In some uses, the term will refer to a thin deposit that substantiallycovers the surface of a substrate it is formed upon. In other morespecialized uses, the term may be used to describe small thin depositsin smaller regions of the surface.

“Electrode” as used herein may refer to an active mass in the energysource. For example, it may include one or both of the anode andcathode.

“Energized” as used herein refers to the state of being able to supplyelectrical current or to have electrical energy stored within.

“Energy” as used herein refers to the capacity of a physical system todo work. Many uses of the energization elements may relate to thecapacity of being able to perform electrical actions.

“Energy Source” or “Energization Element” or “Energization Device” asused herein refers to any device or layer which is capable of supplyingenergy or placing a logical or electrical device in an energized state.The energization elements may include batteries. The batteries may beformed from alkaline type cell chemistry and may be solid-statebatteries or wet cell batteries.

“Fillers” as used herein refer to one or more energization elementseparators that do not react with either acid or alkaline electrolytes.Generally, fillers may include substantially water insoluble materialssuch as carbon black; coal dust; graphite; metal oxides and hydroxidessuch as those of silicon, aluminum, calcium, magnesium, barium,titanium, iron, zinc, and tin; metal carbonates such as those of calciumand magnesium; minerals such as mica, montmorillonite, kaolinite,attapulgite, and talc; synthetic and natural zeolites such as Portlandcement; precipitated metal silicates such as calcium silicate; hollow orsolid polymer or glass microspheres, flakes and fibers; etc.

“Functionalized” as used herein refers to making a layer or device ableto perform a function including, for example, energization, activation,and/or control.

“Mold” as used herein refers to a rigid or semi-rigid object that may beused to form three-dimensional objects from uncured formulations. Someexemplary molds include two mold parts that, when opposed to oneanother, define the structure of a three-dimensional object.

“Power” as used herein refers to work done or energy transferred perunit of time.

“Rechargeable” or “Re-energizable” as used herein refer to a capabilityof being restored to a state with higher capacity to do work. Many usesmay relate to the capability of being restored with the ability to flowelectrical current at a certain rate for certain, reestablished timeperiods.

“Reenergize” or “Recharge” as used herein refer to restoring to a statewith higher capacity to do work. Many uses may relate to restoring adevice to the capability to flow electrical current at a certain ratefor a certain reestablished time period.

“Released” as used herein and sometimes referred to as “released from amold” means that a three-dimensional object is either completelyseparated from the mold, or is only loosely attached to the mold, sothat it may be removed with mild agitation.

“Stacked” as used herein means to place at least two component layers inproximity to each other such that at least a portion of one surface ofone of the layers contacts a first surface of a second layer. In someexamples, a coating, whether for adhesion or other functions, may residebetween the two layers that are in contact with each other through saidcoating.

“Traces” as used herein refer to energization element components capableof connecting together the circuit components. For example, circuittraces may include copper or gold when the substrate is a printedcircuit board and may typically be copper, gold or printed film in aflexible circuit. A special type of “Trace” is the current collector.Current collectors are traces with electrochemical compatibility thatmake the current collectors suitable for use in conducting electrons toand from an anode or cathode in the presence of electrolyte.

The methods and apparatus presented herein relate to formingbiocompatible energization elements for inclusion within or on flat orthree-dimensional biocompatible devices. A particular class ofenergization elements may be batteries that are fabricated in layers.The layers may also be classified as laminate layers. A battery formedin this manner may be classified as a laminar battery.

There may be other examples of how to assemble and configure batteriesaccording to the present invention, and some may be described infollowing sections. However, for many of these examples, there areselected parameters and characteristics of the batteries that may bedescribed in their own right. In the following sections, somecharacteristics and parameters will be focused upon.

Exemplary Biomedical Device Construction with Biocompatible EnergizationElements

An example of a biomedical device that may incorporate the energizationelements, batteries, of the present invention may be an electroactivefocal-adjusting contact lens. Referring to FIG. 1A, an example of such acontact lens insert may be depicted as contact lens insert 100. In thecontact lens insert 100, there may be an electroactive element 120 thatmay accommodate focal characteristic changes in response to controllingvoltages. A circuit 105, to provide those controlling voltage signals aswell as to provide other functions such as controlling sensing of theenvironment for external control signals, may be powered by abiocompatible battery element 110. As depicted in FIG. 1A, the batteryelement 110 may be found as multiple major pieces, in this case threepieces, and may include the various configurations of battery chemistryelements as has been discussed. The battery elements 110 may havevarious interconnect features to join together pieces as may be depictedunderlying the region of interconnect 114. The battery elements 110 maybe connected to a circuit element that may have its own substrate 111upon which interconnect features 125 may be located. The circuit 105,which may be in the form of an integrated circuit, may be electricallyand physically connected to the substrate 111 and its interconnectfeatures 125.

Referring to FIG. 1B, a cross sectional relief of a contact lens 150 maycomprise contact lens insert 100 and its discussed constituents. Thecontact lens insert 100 may be encapsulated into a skirt of contact lenshydrogel 155 which may encapsulate the contact lens insert 100 andprovide a comfortable interface of the contact lens 150 to a user's eye.

In reference to concepts of the present invention, the battery elementsmay be formed in a two-dimensional form as depicted in FIG. 1C. In thisdepiction there may be two main regions of battery cells in the regionsof battery component 165 and the second battery component in the regionof battery chemistry element 160. The battery elements, which aredepicted in flat form in FIG. 1C, may connect to a circuit element 163,which in the example of FIG. 1C may comprise two major circuit areas167. The circuit element 163 may connect to the battery element at anelectrical contact 161 and a physical contact 162. The flat structuremay be folded into a three-dimensional conical structure as has beendescribed with respect to the present invention. In that process asecond electrical contact 166 and a second physical contact 164 may beused to connect and physically stabilize the three-dimensionalstructure. Referring to FIG. 1D, a representation of thisthree-dimensional conical structure 180 may be found. The physical andelectrical contact points 181 may also be found and the illustration maybe viewed as a three-dimensional view of the resulting structure. Thisstructure may include the modular electrical and battery component thatwill be incorporated with a lens insert into a biocompatible device. Theexample of a contact lens demonstrates how a biocompatible battery maybe used in a biomedical device, but the example is not limiting asnumerous other biomedical devices such as electronically active pills,stents, implants, skin tags and bandages, dental implants, wearableelectronic devices and electronically active apparel and shoes may benon-limiting examples of biomedical devices where biocompatible polymerelectrolytes batteries of the present disclosure may be utilized.

A Planar Polymer Electrolyte Battery Example

Referring to FIG. 2, an example of a planar polymer electrolyte batteryis depicted in cross section. In later sections of the disclosure thecomponents and methods for their assembly are discussed, but the crosssection gives an example of how significant battery components may beorganized for polymer electrolyte primary batteries. The battery mayhave cathode regions, anode regions, separator and electrolyte regionsand encapsulation. A cathode current collector 220 may form a base ofthe device. The cathode current collector 220 may be a conductive metalpiece formed from materials such as titanium, brass, stainless steel andthe like. The cathode current collector 220 may be coated with variouscoatings to enhance surface binding and lower the resistance; a carboncoating is commonly used. A portion of the cathode current collector 220may be exposed from encapsulation 280 and form a cathode collectorcontact 210. Surface coatings used inside the cell may either not bedeposited in this region or alternatively may be removed to allow foreffective external connection. Surface coatings may also be applied tothe cathode collector contact 210 outside the cell to improveconnections, for example silver epoxy, solder, or flux. The cathode 230may be formed upon the cathode collector 220. The cathode 230 maycomprise numerous components including the electroactive cathodechemistry such as MnO₂ in a non-limiting sense as well as binders,electrolytes, and other additives.

A polymer electrolyte 240 may be formed upon the cathode. In someexamples, the electrolyte may be coated on top of the cathode or theanode. In other examples, the electrolyte may be applied by screenprinting methods or dip coating methods. There may be numerous mannersto apply the polymer electrolyte 240. The polymer electrolyte 240 mayalso function as a separator of the battery device.

On the other surface of the polymer electrolyte 240 may be the anode250. The anode 250 may be a deposited film, a paste, a foil or solidfilm adhered to the polymer electrolyte 240. The anode 250 may beconnected to the anode collector 260. A portion of the anode collector260 may extend past the encapsulation 280 to create the anode collectorcontact 270. There may be numerous manners to form the exemplarystructure depicted and the order of steps may vary; therefore, while afilm may be described as formed upon another layer it may be assumedthat the order may also be reversed. Furthermore, some elements mayoptionally be removed; such as, the anode collector 260 may be the samelayer as the anode 250 in some examples.

Custom Shapes of Flat Battery Elements

In some examples of biocompatible batteries, the batteries may be formedas flat elements. Referring to FIG. 3A, an example of a rectangularoutline 310 of the battery element may be depicted with an anodeconnection 311 and a cathode connection 312. Referring to FIG. 3B, anexample of a circular outline 330 of a battery element may be depictedwith an anode connection 331 and a cathode connection 332.

In some examples of flat-formed batteries, the outlines of the batteryform may be dimensionally and geometrically configured to fit in customproducts. In addition to examples with rectangular or circular outlines,custom “free-form” or “free shape” outlines may be formed which mayallow the battery configuration to be optimized to fit within a givenproduct.

In the exemplary biomedical device case of a variable optic, a“free-form” example of a flat outline may be arcuate in form. The freeform may be of such geometry that when formed to a three-dimensionalshape, it may take the form of a conical, annular skirt that fits withinthe constraining confines of a contact lens. It may be clear thatsimilar beneficial geometries may be formed where medical devices haverestrictive 2D or 3D shape requirements.

Electrical Requirements of Microbatteries

Another area for design considerations may relate to electricalrequirements of the device, which may be provided by the battery. Inorder to function as a power source for a medical device, an appropriatebattery may need to meet the full electrical requirements of the systemwhen operating in a non-connected or non-externally powered mode. Anemerging field of non-connected or non-externally powered biomedicaldevices may include, for example, vision-correcting contact lenses,health monitoring devices, pill cameras, and novelty devices. Recentdevelopments in integrated circuit (IC) technology may permit meaningfulelectrical operation at very low current levels, for example, Pico ampsof standby current and micro amps of operating current. IC's may alsopermit very small devices.

Microbatteries for biomedical applications may be required to meet manysimultaneous, challenging requirements. For example, the microbatterymay be required to have the capability to deliver a suitable operatingvoltage to an incorporated electrical circuit. This operating voltagemay be influenced by several factors including the IC process “node,”the output voltage from the circuit to another device, and a particularcurrent consumption target which may also relate to a desired devicelifetime.

With respect to the IC process, nodes may typically be differentiated bythe minimum feature size of a transistor, such as its “so-called”transistor channel. This physical feature, along with other parametersof the IC fabrication, such as gate oxide thickness, may be associatedwith a resulting rating standard for “turn-on” or “threshold” voltagesof field-effect transistors (FET's) fabricated in the given processnode. For example, in a node with a minimum feature size of 0.5 microns,it may be common to find FET's with turn-on voltages of 5.0V. However,at a minimum feature size of 90 nm, the FET's may turn-on at 1.2, 1.8,and 2.5V. The IC foundry may supply standard cells of digital blocks,for example, inverters and flip-flops that have been characterized andare rated for use over certain voltage ranges. Designers chose an ICprocess node based on several factors including density of digitaldevices, analog/digital mixed signal devices, leakage current, wiringlayers, and availability of specialty devices such as high-voltageFET's. Given these parametric aspects of the electrical components,which may draw power from a microbattery, it may be important for themicrobattery power source to be matched to the requirements of thechosen process node and IC design, especially in terms of availablevoltage and current.

In some examples, an electrical circuit powered by a microbattery, mayconnect to another device. In non-limiting examples, themicrobattery-powered electrical circuit may connect to an actuator or atransducer. Depending on the application, these may include alight-emitting diode (LED), a sensor, a microelectromechanical system(MEMS) pump, or numerous other such devices. In some examples, suchconnected devices may require higher operating voltage conditions thancommon IC process nodes. For example, a variable-focus lens may require35V to activate. The operating voltage provided by the battery maytherefore be a critical consideration when designing such a system. Insome examples of this type of consideration, the efficiency of a lensdriver to produce 35V from a 1V battery may be significantly less thanit might be when operating from a 2V battery. Further requirements, suchas die size, may be dramatically different considering the operatingparameters of the microbattery as well.

Individual battery cells may typically be rated with open-circuit,loaded, and cutoff voltages. The open-circuit voltage is the potentialproduced by the battery cell with infinite load resistance. The loadedvoltage is the potential produced by the cell with an appropriate, andtypically also specified, load impedance placed across the cellterminals. The cutoff voltage is typically a voltage at which most ofthe battery has been discharged. The cutoff voltage may represent avoltage, or degree of discharge, below which the battery should not bedischarged to avoid deleterious effects such as excessive gassing. Thecutoff voltage may typically be influenced by the circuit to which thebattery is connected, not just the battery itself, for example, theminimum operating voltage of the electronic circuit. In one example, analkaline cell may have an open-circuit voltage of 1.6V, a loaded voltagein the range 1.0 to 1.5V, and a cutoff voltage of 1.0V. The voltage of agiven microbattery cell design may depend upon other factors of the cellchemistry employed. And, different cell chemistry may therefore havedifferent cell voltages.

Cells may be connected in series to increase voltage; however, thiscombination may come with tradeoffs to size, internal resistance, andbattery complexity. Cells may also be combined in parallelconfigurations to decrease resistance and increase capacity; however,such a combination may tradeoff size and shelf life.

Battery capacity may be the ability of a battery to deliver current, ordo work, for a period of time. Battery capacity may typically bespecified in units such as micro amp-hours. A battery that may deliver 1micro amp of current for 1 hour has 1 micro amp-hour of capacity.Capacity may typically be increased by increasing the mass (and hencevolume) of reactants within a battery device; however, it may beappreciated that biomedical devices may be significantly constrained onavailable volume. Battery capacity may also be influenced by electrodeand electrolyte material.

Depending on the requirements of the circuitry to which the battery isconnected, a battery may be required to source current over a range ofvalues. During storage prior to active use, a leakage current on theorder of Pico amps to nan amps may flow through circuits, interconnects,and insulators. During active operation, circuitry may consume quiescentcurrent to sample sensors, run timers, and perform such low powerconsumption functions. Quiescent current consumption may be on the orderof nano amps to milliamps. Circuitry may also have even higher peakcurrent demands, for example, when writing flash memory or communicatingover radio frequency (RF). This peak current may extend to tens ofmilliamps or more. The resistance and impedance of a microbattery devicemay also be important to design considerations.

Shelf life typically refers to the period of time which a battery maysurvive in storage and still maintain useful operating parameters. Shelflife may be particularly important for biomedical devices for severalreasons. Electronic devices may displace non-powered devices, as forexample may be the case for the introduction of an electronic contactlens. Products in these existing market spaces may have establishedshelf life requirements, for example, three years, due to customer,supply chain, and other requirements. It may typically be desired thatsuch specifications not be altered for new products. Shelf liferequirements may also be set by the distribution, inventory, and usemethods of a device including a microbattery. Accordingly,microbatteries for biomedical devices may have specific shelf liferequirements, which may be, for example, measured in the number ofyears.

In some examples, three-dimensional biocompatible energization elementsmay be rechargeable. For example, an inductive coil may also befabricated on the three-dimensional surface. The inductive coil couldthen be energized with a radio-frequency (“RF”) fob. The inductive coilmay be connected to the three-dimensional biocompatible energizationelement to recharge the energization element when RF is applied to theinductive coil. In another example, photovoltaics may also be fabricatedon the three-dimensional surface and connected to the three-dimensionalbiocompatible energization element. When exposed to light or photons,the photovoltaics will produce electrons to recharge the energizationelement.

In some examples, a battery may function to provide the electricalenergy for an electrical system. In these examples, the battery may beelectrically connected to the circuit of the electrical system. Theconnections between a circuit and a battery may be classified asinterconnects. These interconnects may become increasingly challengingfor biomedical microbatteries due to several factors. In some examples,powered biomedical devices may be very small thus allowing little areaand volume for the interconnects. The restrictions of size and area mayimpact the electrical resistance and reliability of theinterconnections.

In other respects, a battery may contain a liquid electrolyte whichcould boil at high temperature. This restriction may directly competewith the desire to use a solder interconnect which may, for example,require relatively high temperatures such as 250 degrees Celsius tomelt. Although in some examples, the battery chemistry, including theelectrolyte, and the heat source used to form solder basedinterconnects, may be isolated spatially from each other. In the casesof emerging biomedical devices, the small size may preclude theseparation of electrolyte and solder joints by sufficient distance toreduce heat conduction.

Interconnects

Interconnects may allow current to flow to and from the battery inconnection with an external circuit. Such interconnects may interfacewith the environments inside and outside the battery, and may cross theboundary or seal between those environments. These interconnects may beconsidered as traces, making connections to an external circuit, passingthrough the battery seal, and then connecting to the current collectorsinside the battery. As such, these interconnects may have severalrequirements. Outside the battery, the interconnects may resembletypical printed circuit traces. They may be soldered to, or otherwiseconnect to, other traces. In an example, where the battery is a separatephysical element from a circuit board comprising an integrated circuit,the battery interconnect may allow for connection to the externalcircuit. This connection may be formed with solder, conductive tape,conductive ink or epoxy, or other means. The interconnect traces mayneed to survive in the environment outside the battery, for example, notcorroding in the presence of oxygen.

As the interconnect passes through the battery seal, it may be ofcritical importance that the interconnect coexist with the seal andpermit sealing. Adhesion may be required between the seal andinterconnect in addition to the adhesion which may be required betweenthe seal and battery package. Seal integrity may need to be maintainedin the presence of electrolyte and other materials inside the battery.Interconnects, which may typically be metallic, may be known as pointsof failure in battery packaging. The electrical potential and/or flow ofcurrent may increase the tendency for electrolyte to “creep” along theinterconnect. Accordingly, an interconnect may need to be engineered tomaintain seal integrity.

Inside the battery, the interconnects may interface with the currentcollectors or may actually form the current collectors. In this regard,the interconnect may need to meet the requirements of the currentcollectors as described herein, or may need to form an electricalconnection to such current collectors.

One class of candidate interconnects and current collectors are metalfoils. Such foils are available in thickness of 25 microns or less,which make them suitable for very thin batteries. Such foil may also besourced with low surface roughness and contamination, two factors whichmay be critical for battery performance. The foils may include zinc,nickel, brass, copper, titanium, other metals, and various alloys.

Modular Battery Components

In some examples, a modular battery component may be formed according tosome aspects and examples of the present invention. In these examples,the modular battery assembly may be a separate component from otherparts of the biomedical device. In the example of an ophthalmic contactlens device, such a design may include a modular battery that isseparate from the rest of a media insert. There may be numerousadvantages of forming a modular battery component. For example, in theexample of the contact lens, a modular battery component may be formedin a separate, non-integrated process which may alleviate the need tohandle rigid, three-dimensionally formed optical plastic components. Inaddition, the sources of manufacturing may be more flexible and mayoperate in a more parallel mode to the manufacturing of the othercomponents in the biomedical device. Furthermore, the fabrication of themodular battery components may be decoupled from the characteristics ofthree-dimensional (3D) shaped devices. For example, in applicationsrequiring three-dimensional final forms, a modular battery system may befabricated in a flat or roughly two-dimensional (2D) perspective andthen shaped to the appropriate three-dimensional shape. A modularbattery component may be tested independently of the rest of thebiomedical device and yield loss due to battery components may be sortedbefore assembly. The resulting modular battery component may be utilizedin various media insert constructs that do not have an appropriate rigidregion upon which the battery components may be formed; and, in a stillfurther example, the use of modular battery components may facilitatethe use of different options for fabrication technologies than mightotherwise be utilized, such as, web-based technology (roll to roll),sheet-based technology (sheet-to-sheet), printing, lithography, and“squeegee” processing. In some examples of a modular battery, thediscrete containment aspect of such a device may result in additionalmaterial being added to the overall biomedical device construct. Sucheffects may set a constraint for the use of modular battery solutionswhen the available space parameters require minimized thickness orvolume of solutions.

Battery shape requirements may be driven at least in part by theapplication for which the battery is to be used. Traditional batteryform factors may be cylindrical forms or rectangular prisms, made ofmetal, and may be geared toward products which require large amounts ofpower for long durations. These applications may be large enough thatthey may comprise large form factor batteries. In another example,planar (2D) solid-state batteries are thin rectangular prisms, typicallyformed upon inflexible silicon or glass. These planar solid-statebatteries may be formed in some examples using silicon wafer-processingtechnologies. In another type of battery form factor, low power,flexible batteries may be formed in a pouch construct, using thin foilsor plastic to contain the battery chemistry. These batteries may be madeflat (2D), and may be designed to function when bowed to a modestout-of-plane (3D) curvature.

In some of the examples of the battery applications in the presentinvention where the battery may be employed in a variable optic lens,the form factor may require a three-dimensional curvature of the batterycomponent where a radius of that curvature may be on the order ofapproximately 8.4 mm. The nature of such a curvature may be consideredto be relatively steep and for reference may approximate the type ofcurvature found on a human fingertip. The nature of a relative steepcurvature creates challenging aspects for manufacture. In some examplesof the present invention, a modular battery component may be designedsuch that it may be fabricated in a flat, two-dimensional manner andthen formed into a three-dimensional form of relative high curvature.

Battery Module Thickness

In designing battery components for biomedical applications, tradeoffsamongst the various parameters may be made balancing technical, safetyand functional requirements. The thickness of the battery component maybe an important and limiting parameter. For example, in an optical lensapplication the ability of a device to be comfortably worn by a user mayhave a critical dependence on the thickness across the biomedicaldevice. Therefore, there may be critical enabling aspects in designingthe battery for thinner results. In some examples, battery thickness maybe determined by the combined thicknesses of top and bottom sheets,spacer sheets, and adhesive layer thicknesses. Practical manufacturingaspects may drive certain parameters of film thickness to standardvalues in available sheet stock. In addition, the films may have minimumthickness values to which they may be specified base upon technicalconsiderations relating to chemical compatibility, moisture/gasimpermeability, surface finish, and compatibility with coatings that maybe deposited upon the film layers.

In some examples, a desired or goal thickness of a finished batterycomponent may be a component thickness that is less than 220 μm. Inthese examples, this desired thickness may be driven by thethree-dimensional geometry of an exemplary ophthalmic lens device wherethe battery component may need to be fit inside the available volumedefined by a hydrogel lens shape given end user comfort,biocompatibility, and acceptance constraints. This volume and its effecton the needs of battery component thickness may be a function of totaldevice thickness specification as well as device specification relatingto its width, cone angle, and inner diameter. Another important designconsideration for the resulting battery component design may relate tothe volume available for active battery chemicals and materials in agiven battery component design with respect to the resulting chemicalenergy that may result from that design. This resulting chemical energymay then be balanced for the electrical requirements of a functionalbiomedical device for its targeted life and operating conditions

Battery Module Flexibility

Another dimension of relevance to battery design and to the design ofrelated devices that utilize battery based energy sources is theflexibility of the battery component. There may be numerous advantagesconferred by flexible battery forms. For example, a flexible batterymodule may facilitate the previously mentioned ability to fabricate thebattery form in a two-dimensional (2D) flat form. The flexibility of theform may allow the two-dimensional battery to then be formed into anappropriate 3D shape to fit into a biomedical device such as a contactlens.

In another example of the benefits that may be conferred by flexibilityin the battery module, if the battery and the subsequent device isflexible then there may be advantages relating to the use of the device.In an example, a contact lens form of a biomedical device may haveadvantages for insertion/removal of the media insert based contact lensthat may be closer to the insertion/removal of a standard, non-filledhydrogel contact lens.

The number of flexures may be important to the engineering of thebattery. For example, a battery which may only flex one time from aplanar form into a shape suitable for a contact lens may havesignificantly different design from a battery capable of multipleflexures. The flexure of the battery may also extend beyond the abilityto mechanically survive the flexure event. For example, an electrode maybe physically capable of flexing without breaking, but the mechanicaland electrochemical properties of the electrode may be altered byflexure. Flex-induced changes may appear instantly, for example, aschanges to impedance, or flexure may introduce changes which are onlyapparent in long-term shelf life testing.

Battery Module Width

There may be numerous applications into which the biocompatibleenergization elements or batteries of the present invention may beutilized. In general, the battery width requirement may be largely afunction of the application in which it is applied. In an exemplarycase, a contact lens battery system may have constrained needs for thespecification on the width of a modular battery component. In someexamples of an ophthalmic device where the device has a variable opticfunction powered by a battery component, the variable optic portion ofthe device may occupy a central spherical region of about 7.0 mm indiameter. The exemplary battery elements may be considered as athree-dimensional object, which fits as an annular, conical skirt aroundthe central optic and formed into a truncated conical ring. If therequired maximum diameter of the rigid insert is a diameter of 8.50 mm,and tangency to a certain diameter sphere may be targeted (as forexample in a roughly 8.40 mm diameter), then geometry may dictate whatthe allowable battery width may be. There may be geometric models thatmay be useful for calculating desirable specifications for the resultinggeometry which in some examples may be termed a conical frustumflattened into a sector of an annulus.

Flattened battery width may be driven by two features of the batteryelement, the active battery components and seal width. In some examplesrelating to ophthalmic devices a target thickness may be between 0.100mm and 0.500 mm per side, and the active battery components may betargeted at approximately 0.800 mm wide. Other biomedical devices mayhave differing design constraints but the principles for flexible flatbattery elements may apply in similar fashion.

Battery Element Internal Seals

It may be important in examples of polymer electrolyte batteries toincorporate sealing mechanisms that retard or prevent the movement ofmoisture or other chemicals into the battery body. Moisture barriers maybe designed to keep the internal moisture level at a designed level,within some tolerance. In some examples, a moisture barrier may bedivided into two sections or components; namely, the package and theseal. Polymer electrolytes may have an inherent advantage in that anyleaking of moisture into the polymer electrolyte from external regionsmay have minimal impact, and may even improve battery performance insome examples. Thus, the importance of packaging requirements may beinherently reduced for polymer electrolyte batteries.

Nevertheless, the package may refer to the main material of theenclosure. In some examples, the package may comprise a bulk material.The Water Vapor Transmission Rate (WVTR) may be an indicator ofperformance, with ISO, ASTM standards controlling the test procedure,including the environmental conditions operant during the testing.Ideally, the WVTR for a good battery package may be “zero.” Exemplarymaterials with a near-zero WVTR may be glass and metal foils. Plastics,on the other hand, may be inherently porous to moisture, and may varysignificantly for different types of plastic. Engineered materials,laminates, or co-extrudes may usually be hybrids of the common packagematerials.

The seal may be the interface between two of the package surfaces. Theconnecting of seal surfaces finishes the enclosure along with thepackage. In many examples, the nature of seal designs may make themdifficult to characterize for the seal's WVTR due to difficulty inperforming measurements using an ISO or ASTM standard, as the samplesize or surface area may not be compatible with those procedures. Insome examples, a practical manner to testing seal integrity may be afunctional test of the actual seal design, for some defined conditions.Seal performance may be a function of the seal material, the sealthickness, the seal length, the seal width, and the seal adhesion orintimacy to package substrates.

In some examples, seals may be formed by a welding process that mayinvolve thermal, laser, solvent, friction, ultrasonic, or arcprocessing. In other examples, seals may be formed through the use ofadhesive sealants such as glues, epoxies, acrylics, natural rubber, andsynthetic rubber. Other examples may derive from the utilization ofgasket type material that may be formed from cork, natural and syntheticrubber, polytetrafluoroethylene (PTFE), polypropylene, and silicones tomention a few non-limiting examples.

In some examples, the batteries according to the present invention maybe designed to have a specified operating life. The operating life maybe estimated by determining a practical amount of moisture permeabilitythat may be obtained using a particular battery system and thenestimating when such a moisture leakage may result in an end of lifecondition for the battery.

Additional Package and Substrate Considerations in Biocompatible BatteryModules

There may be numerous packaging and substrate considerations that maydictate desirable characteristics for package designs used inbiocompatible laminar microbatteries. For example, the packaging maydesirably be predominantly foil and/or film based where these packaginglayers may be as thin as possible, for example, 10 to 50 microns.Additionally, the packaging may provide a sufficient diffusion barrierto moisture gain or loss during the shelf life. In many desirableexamples, the packaging may provide a sufficient diffusion barrier tooxygen ingress to limit degradation of zinc anodes by direct oxidation.

In some examples, the packaging may provide a finite permeation pathwayto hydrogen gas that may evolve due to direct reduction of water byzinc. And, the packaging may desirably sufficiently contain and mayisolate the contents of the battery such that potential exposure to auser may be minimized.

In the present invention, packaging constructs may include the followingtypes of functional components: top and bottom packaging layers,pressure sensitive adhesive (PSA) layers, spacer layers, interconnectzones, filling ports, and secondary packaging.

In some examples, top and bottom packaging layers may comprise metallicfoils or polymer films. Top and bottom packaging layers may comprisemulti-layer film constructs containing a plurality of polymer and/orbarrier layers. Such film constructs may be referred to as coextrudedbarrier laminate films. An example of a commercial coextruded barrierlaminate film of particular utility in the present invention may be 3M®Scotchpak 1109 backing which consists of a polyethylene terephthalate(PET) carrier web, a vapor-deposited aluminum barrier layer, and apolyethylene layer including a total average film thickness of 33microns. Numerous other similar multilayer barrier films may beavailable and may be used in alternate examples of the presentinvention.

In design constructions including a PSA, packaging layer surfaceroughness may be of particular importance because the PSA may also needto seal opposing packaging layer faces. Surface roughness may resultfrom manufacturing processes used in foil and film production, forexample, processes employing rolling, extruding, embossing and/orcalendaring, among others. If the surface is too rough, PSA may be notable to be applied in a uniform thickness when the desired PSA thicknessmay be on the order of the surface roughness Ra (the arithmetic averageof the roughness profile). Furthermore, PSA's may not adequately sealagainst an opposing face if the opposing face has roughness that may beon the order of the PSA layer thickness. In the present invention,packaging materials having a surface roughness, Ra, less than 10 micronsmay be acceptable examples. In some examples, surface roughness valuesmay be 5 microns or less. And, in still further examples, the surfaceroughness may be 1 micron or less. Surface roughness values may bemeasured by a variety of methods including but not limited tomeasurement techniques such as white light interferometry, stylusprofilometry, and the like. There may be many examples in the art ofsurface metrology that surface roughness may be described by a number ofalternative parameters and that the average surface roughness, Ra,values discussed herein may be meant to be representative of the typesof features inherent in the aforementioned manufacturing processes.

Current Collectors and Electrodes

In some examples of zinc carbon and Leclanche cells, the cathode currentcollector may be a sintered carbon rod. This type of material may facetechnical hurdles for thin electrochemical cells of the presentinvention. In some examples, printed carbon inks may be used in thinelectrochemical cells to replace a sintered carbon rod for the cathodecurrent collector, and in these examples, the resulting device may beformed without significant impairment to the resulting electrochemicalcell. Typically, said carbon inks may be applied directly to packagingmaterials which may comprise polymer films, or in some cases metalfoils. In the examples where the packaging film may be a metal foil, thecarbon ink may need to protect the underlying metal foil from chemicaldegradation and/or corrosion by the electrolyte. Furthermore, in theseexamples, the carbon ink current collector may need to provideelectrical conductivity from the inside of the electrochemical cell tothe outside of the electrochemical cell, implying sealing around orthrough the carbon ink. Due to the porous nature of carbon inks, thismay be not easily accomplished without significant challenges. Carboninks also may be applied in layers that have finite and relatively smallthickness, for example, 10 to 20 microns. In a thin electrochemical celldesign in which the total internal package thickness may only be about100 to 150 microns, the thickness of a carbon ink layer may take up asignificant fraction of the total internal volume of the electrochemicalcell, thereby negatively impacting electrical performance of the cell.Further, the thin nature of the overall battery and the currentcollector in particular may imply a small cross-sectional area for thecurrent collector. As resistance of a trace increases with trace lengthand decreases with cross-sectional area, there may be a direct tradeoffbetween current collector thickness and resistance. The bulk resistivityof carbon ink may be insufficient to meet the resistance requirement ofthin batteries. Inks filled with silver or other conductive metals mayalso be considered to decrease resistance and/or thickness, but they mayintroduce new challenges such as incompatibility with novelelectrolytes. In consideration of these factors, in some examples it maybe desirable to realize efficient and high performance thinelectrochemical cells of the present invention by utilizing a thin metalfoil as the current collector, or to apply a thin metal film to anunderlying polymer packaging layer to act as the current collector. Suchmetal foils may have significantly lower resistivity, thereby allowingthem to meet electrical resistance requirements with much less thicknessthan printed carbon inks.

In some examples, one or more of the top and/or bottom packaging layersmay serve as a substrate for a sputtered current collector metal ormetal stack. For example, 3M® Scotchpak 1109 backing may be metallizedusing physical vapor deposition (PVD) of one or more metallic layersuseful as a current collector for a cathode. Exemplary metal stacksuseful as cathode current collectors may be Ti—W (titanium-tungsten)adhesion layers and Ti (titanium) conductor layers. Exemplary metalstacks useful as anode current collectors may be Ti—W adhesion layers,Au (gold) conductor layers, and In (indium) deposition layers. Thethickness of the PVD layers may be less than 500 nm in total. Ifmultiple layers of metals are used, the electrochemical and barrierproperties may need to be compatible with the battery. For example,copper may be electroplated on top of a seed layer to grow a thick layerof conductor. Additional layers may be plated upon the copper. However,copper may be electrochemically incompatible with certain electrolytesespecially in the presence of zinc. Accordingly, if copper is used as alayer in the battery, it may need to be sufficiently isolated from thebattery electrolyte. Alternatively, copper may be excluded or anothermetal substituted.

In some other examples, top and/or bottom packaging foils may alsofunction as current collectors. For example, a 25 micron brass foil maybe useful as an anode current collector for a zinc anode. The brass foilmay be optionally electroplated with indium prior to electroplating withzinc. In one example, cathode current collector packaging foils maycomprise titanium foil, Hastelloy C-276 foil, chromium foil, and/ortantalum foil. In certain designs, one or more packaging foils may befine blanked, embossed, etched, textured, laser machined, or otherwiseprocessed to provide desirable form, surface roughness, and/or geometryto the final cell packaging.

Cathode Mixture

There may be numerous cathode chemistry mixtures that may be consistentwith the concepts of the present invention. In some examples, a cathodemixture, which may be a term for a chemical formulation used to form abattery's cathode, may be applied as a paste, gel, suspension, orslurry, and may comprise a transition metal oxide such as manganesedioxide, some form of conductive additive which, for example, may be aform of conductive powder such as carbon black or graphite, and awater-soluble polymer such as polyvinylpyrrolidone (PVP) or some otherbinder additive. In some examples, other components may be included suchas one or more of binders, electrolyte salts, corrosion inhibitors,water or other solvents, surfactants, rheology modifiers, and otherconductive additives, such as, conductive polymers. Once formulated andappropriately mixed, the cathode mixture may have a desirable rheologythat allows it to either be dispensed onto desired portions of theseparator and/or cathode current collector, or squeegeed through ascreen or stencil in a similar manner. In some examples, the cathodemixture may be dried before being used in later cell assembly steps,while in other examples, the cathode may contain some or all of theelectrolyte components, and may only be partially dried to a selectedmoisture content.

The transition metal oxide may, for example, be manganese dioxide. Themanganese dioxide which may be used in the cathode mixture may be, forexample, electrolytic manganese dioxide (EMD) due to the beneficialadditional specific energy that this type of manganese dioxide providesrelative to other forms, such as natural manganese dioxide (NMD) orchemical manganese dioxide (CMD). Furthermore, the EMD useful inbatteries of the present invention may need to have a particle size andparticle size distribution that may be conducive to the formation ofdepositable or printable cathode mixture pastes/slurries. Specifically,the EMD may be processed to remove significant large particulatecomponents that may be considered large relative to other features suchas battery internal dimensions, separator thicknesses, dispense tipdiameters, stencil opening sizes, or screen mesh sizes. Particle sizeoptimization may also be used to improve performance of the battery, forexample, internal impedance and discharge capacity.

Milling is the reduction of solid materials from one average particlesize to a smaller average particle size, by crushing, grinding, cutting,vibrating, or other processes. Milling may also be used to free usefulmaterials from matrix materials in which they may be embedded, and toconcentrate minerals. A mill is a device that breaks solid materialsinto smaller pieces by grinding, crushing, or cutting. There may beseveral means for milling and many types of materials processed in them.Such means of milling may include: ball mill, bead mill, mortar andpestle, roller press, and jet mill among other milling alternatives. Oneexample of milling may be jet milling. After the milling, the state ofthe solid is changed, for example, the particle size, the particle sizedisposition and the particle shape. Aggregate milling processes may alsobe used to remove or separate contamination or moisture from aggregateto produce “dry fills” prior to transport or structural filling. Someequipment may combine various techniques to sort a solid material into amixture of particles whose size is bounded by both a minimum and maximumparticle size. Such processing may be referred to as “classifiers” or“classification.”

Milling may be one aspect of cathode mixture production for uniformparticle size distribution of the cathode mixture ingredients. Uniformparticle size in a cathode mixture may assist in viscosity, rheology,electroconductivity, and other properties of a cathode. Milling mayassist these properties by controlling agglomeration, or a masscollection, of the cathode mixture ingredients. Agglomeration—theclustering of disparate elements, which in the case of the cathodemixture, may be carbon allotropes and transition metal oxides—maynegatively affect the filling process by leaving voids in the desiredcathode cavity.

Also, filtration may be another important step for the removal ofagglomerated or unwanted particles. Unwanted particles may includeover-sized particles, contaminates, or other particles not explicitlyaccounted for in the preparation process. Filtration may be accomplishedby means such as filter-paper filtration, vacuum filtration,chromatography, microfiltration, and other means of filtration.

In some examples, EMD may have an average particle size of 7 micronswith a large particle content that may contain particulates up to about70 microns. In alternative examples, the EMD may be sieved, furthermilled, or otherwise separated or processed to limit large particulatecontent to below a certain threshold, for example, 25 microns orsmaller.

The cathode may also comprise silver dioxide or nickel oxyhydroxide.Such materials may offer increased capacity and less decrease in loadedvoltage during discharge relative to manganese dioxide, both desirableproperties in a battery. Batteries based on these cathodes may havecurrent examples present in industry and literature. A novelmicrobattery utilizing a silver dioxide cathode may include abiocompatible electrolyte, for example, one comprising zinc chlorideand/or ammonium chloride instead of potassium hydroxide.

Some examples of the cathode mixture may include a polymeric binder. Thebinder may serve a number of functions in the cathode mixture. Theprimary function of the binder may be to create a sufficientinter-particle electrical network between EMD particles and carbonparticles. A secondary function of the binder may be to facilitatemechanical adhesion and electrical contact to the cathode currentcollector. A third function of the binder may be to influence therheological properties of the cathode mixture for advantageousdispensing and/or stenciling/screening. Still, a fourth function of thebinder may be to enhance the electrolyte uptake and distribution withinthe cathode.

The choice of the binder polymer as well as the amount to be used may bebeneficial to the function of the cathode in the electrochemical cell ofthe present invention. If the binder polymer is too soluble in theelectrolyte to be used, then the primary function of thebinder—electrical continuity—may be drastically impacted to the point ofcell non-functionality. On the contrary, if the binder polymer isinsoluble in the electrolyte to be used, portions of EMD may beionically insulated from the electrolyte, resulting in diminished cellperformance such as reduced capacity, lower open circuit voltage, and/orincreased internal resistance.

The binder may be hydrophobic; it may also be hydrophilic. Examples ofbinder polymers useful for the present invention comprise PVP,polyisobutylene (PIB), rubbery triblock copolymers comprising styreneend blocks such as those manufactured by Kraton Polymers,styrene-butadiene latex block copolymers, polyacrylic acid,hydroxyethylcellulose, carboxymethylcellulose, fluorocarbon solids suchas polytetrafluoroethylene, among others.

A solvent may be one component of the cathode mixture. A solvent may beuseful in wetting the cathode mixture, which may assist in the particledistribution of the mixture. One example of a solvent may be toluene.Also, a surfactant may be useful in wetting, and thus distribution, ofthe cathode mixture. One example of a surfactant may be a detergent,such as Triton™ QS-44. Triton™ QS-44 may assist in the dissociation ofaggregated ingredients in the cathode mixture, allowing for a moreuniform distribution of the cathode mixture ingredients.

A conductive carbon may typically be used in the production of acathode. Carbon is capable of forming many allotropes, or differentstructural modifications. Different carbon allotropes have differentphysical properties allowing for variation in electroconductivity. Forexample, the “springiness” of carbon black may help with adherence of acathode mixture to a current collector. However, in energizationelements requiring relatively low amounts of energy, these variations inelectroconductivity may be less important than other favorableproperties such as density, particle size, heat conductivity, andrelative uniformity, among other properties. Examples of carbonallotropes include: diamond, graphite, graphene, amorphous carbon(informally called carbon black), buckminsterfullerenes, glassy carbon(also called vitreous carbon), carbon aerogels, and other possible formsof carbon capable of conducting electricity. One example of a carbonallotrope may be graphite.

Once the cathode mixture has been formulated and processed, the mixturemay be dispensed, applied, and/or stored onto a surface such as thehydrogel separator, or the cathode current collector, or into a volumesuch as the cavity in the laminar structure. Filing onto a surface mayresult in a volume being filled over time. In order to apply, dispense,and/or store the mixture, a certain rheology may be desired to optimizethe dispensing, applying, and/or storing process. For example, a lessviscous rheology may allow for better filling of the cavity while at thesame time possibly sacrificing particle distribution. A more viscousrheology may allow for optimized particle distribution, while possiblydecreasing the ability to fill the cavity and possibly losingelectroconductivity.

Anodes and Anode Corrosion Inhibitors

The anode for the laminar battery of the present invention may, forexample, comprise zinc. In traditional zinc-carbon batteries, a zincanode may take the physical form of a can in which the contents of theelectrochemical cell may be contained. For the battery of the presentinvention, a zinc may be an example but there may be other physicalforms of zinc that may prove desirable to realize ultra-small batterydesigns.

Electroplating of zinc is a process type in numerous industrial uses,for example, for the protective or aesthetic coating of metal parts. Insome examples, electroplated zinc may be used to form thin and conformalanodes useful for batteries of the present invention. Furthermore, theelectroplated zinc may be patterned in many different configurations,depending on the design intent. A facile means for patterningelectroplated zinc may be processing with the use of a photomask or aphysical mask. In the case of the photomask, a photoresist may beapplied to a conductive substrate, the substrate on which zinc maysubsequently be plated. The desired plating pattern may be thenprojected to the photoresist by means of a photomask, thereby causingcuring of selected areas of photoresist. The uncured photoresist maythen be removed with appropriate solvent and cleaning techniques. Theresult may be a patterned area of conductive material that may receivean electroplated zinc treatment. While this method may provide benefitto the shape or design of the zinc to be plated, the approach mayrequire use of available photopatternable materials, which may haveconstrained properties to the overall cell package construction.Consequently, new and novel methods for patterning zinc may be requiredto realize some designs of thin microbatteries of the present invention.

An alternative means of patterning zinc anodes may be by means of aphysical mask application. A physical mask may be made by cuttingdesirable apertures in a film having desirable barrier and/or packagingproperties. Additionally, the film may have pressure-sensitive adhesiveapplied to one or both sides. Finally, the film may have protectiverelease liners applied to one or both adhesives. The release liner mayserve the dual purpose of protecting the adhesive during aperturecutting and protecting the adhesive during specific processing steps ofassembling the electrochemical cell, specifically the cathode fillingstep. In some examples, a zinc mask may comprise a PET film ofapproximately 100 microns thickness to which a pressure-sensitiveadhesive may be applied to both sides in a layer thickness ofapproximately 10-20 microns. Both PSA layers may be covered by a PETrelease film which may have a low surface energy surface treatment, andmay have an approximate thickness of 50 microns. In these examples, themulti-layer zinc mask may comprise PSA and PET film. PET films andPET/PSA zinc mask constructs as described herein may be desirablyprocessed with precision nanosecond laser micromachining equipment, suchas, Oxford Lasers E-Series laser micromachining workstation, to createultra-precise apertures in the mask to facilitate later plating. Inessence, once the zinc mask has been fabricated, one side of the releaseliner may be removed, and the mask with apertures may be laminated tothe anode current collector and/or anode-side packaging film/foil. Inthis manner, the PSA creates a seal at the inside edges of theapertures, facilitating clean and precise masking of the zinc duringelectroplating.

The zinc mask may be placed and then electroplating of one or moremetallic materials may be performed. In some examples, zinc may beelectroplated directly onto an electrochemically compatible anodecurrent collector foil such as brass. In alternate design examples wherethe anode side packaging comprises a polymer film or multi-layer polymerfilm upon which seed metallization has been applied, zinc, and/or theplating solutions used for depositing zinc, may not be chemicallycompatible with the underlying seed metallization. Manifestations oflack of compatibility may include film cracking, corrosion, and/orexacerbated H₂ evolution upon contact with cell electrolyte. In such acase, additional metals may be applied to the seed metal to affectbetter overall chemical compatibility in the system. One metal that mayfind particular utility in electrochemical cell constructions may beindium. Indium may be widely used as an alloying agent in battery gradezinc with its primary function being to provide an anti-corrosionproperty to the zinc in the presence of electrolyte. In some examples,indium may be successfully deposited on various seed metallizations suchas Ti—W and Au. Resulting films of 1-3 microns of indium on said seedmetallization layers may be low-stress and adherent. In this manner, theanode-side packaging film and attached current collector having anindium top layer may be conformable and durable. In some examples, itmay be possible to deposit zinc on an indium-treated surface, theresulting deposit may be very non-uniform and nodular. This effect mayoccur at lower current density settings, for example, 20 amps per squarefoot (ASF). As viewed under a microscope, nodules of zinc may beobserved to form on the underlying smooth indium deposit. In certainelectrochemical cell designs, the vertical space allowance for the zincanode layer may be up to about 5-10 microns thick, but in some examples,lower current densities may be used for zinc plating, and the resultingnodular growths may grow taller than the desired maximum anode verticalthickness. It may be that the nodular zinc growth stems from acombination of the high overpotential of indium and the presence of anoxide layer of indium.

In some examples, higher current density DC plating may overcome therelatively large nodular growth patterns of zinc on indium surfaces. Forexample, 100 ASF plating conditions may result in nodular zinc, but thesize of the zinc nodules may be drastically reduced compared to 20 ASFplating conditions. Furthermore, the number of nodules may be vastlygreater under 100 ASF plating conditions. The resulting zinc film mayultimately coalesce to a more or less uniform layer with only someresidual feature of nodular growth while meeting the vertical spaceallowance of about 5-10 microns.

An added benefit of indium in the electrochemical cell may be reductionof H₂ formation, which may be a slow process that occurs in aqueouselectrochemical cells containing zinc. The indium may be beneficiallyapplied to one or more of the anode current collector, the anode itselfas a co-plated alloying component, or as a surface coating on theelectroplated zinc. For the latter case, indium surface coatings may bedesirably applied in-situ by way of an electrolyte additive such asindium trichloride or indium acetate. When such additives may be addedto the electrolyte in small concentrations, indium may spontaneouslyplate on exposed zinc surfaces as well as portions of exposed anodecurrent collector.

Zinc and similar anodes commonly used in commercial primary batteriesmay typically be found in sheet, rod, and paste forms. The anode of aminiature, biocompatible battery may be of similar form, e.g. thin foil,or may be plated as previously mentioned. The properties of this anodemay differ significantly from those in existing batteries, for example,because of differences in contaminants or surface finish attributed tomachining and plating processes. Accordingly, the electrodes andelectrolyte may require special engineering to meet capacity, impedance,and shelf life requirements. For example, special plating processparameters, plating bath composition, surface treatment, and electrolytecomposition may be needed to optimize electrode performance.Polymer Electrolytes and Separators

There may be a number of different types of electrolyte formulationsthat are consistent with a polymer battery system. In a first class ofexamples, the electrolyte may be called a polymer electrolyte. In thepolymer electrolyte systems the polymer backbone has regions that becomeinvolved in the conduction mechanisms of the ions. As well, theseregions of the polymer backbone also facilitate the dissolution of thesalt ions into the electrolyte bulk. In general, higher levels ofdissolved ions in an electrolyte bulk may result in better batteryperformance characteristics. There may be numerous polymer and copolymersystems utilized to form the polymer backbone of the polymer electrolytesystems. In a non-limiting example polyethylene oxide (PEO) may be acommon polymer constituent. The ionic conductivity of the system mayimprove at higher operating temperature conditions, but may berelatively poor at room temperature operating conditions. In someexamples a sheet form of a polymer electrolyte may be formed includingthe presence of ionic species. The sheet form may be applied to anelectrode with high temperature lamination processing. In otherexamples, the electrolyte formulation may be coated upon an electrodesurface. Each of these processing options may be useful to enhance thebinding of the electrolyte to electrodes which may generally result inpoor adhesion under other processing conditions.

In another class of examples, plasticized polymer electrolytes may beutilized in polymer electrolyte battery systems. There may be manypolymer systems that may be useful to form plasticized polymerelectrolytes including as non-limiting examples PEO, poly(methylmethacrylate) (PMMA) and poly(vinyl chloride) amongst other polymersystems. The selected polymer backbone creates a two-dimensional orthree-dimensional matrix into which a solvent and ionic solute systemmay be incorporated. The incorporation of the solvent system withdissolved ionic species “plasticizes” the polymer electrolyte. Unlikethe first class of polymer electrolyte systems, the backbone of aplasticized polymer electrolyte system may not participate in the ionictransport across the electrolyte. The presence of the solvent is anotherdifference from the first class of polymer electrolyte systems and doesact to facilitate ionic transfer. In some examples, the ionic transportand related ionic conductivities of the battery structure may be higherin a plasticized polymer electrolyte system for these reasons. In someexamples, the matrix of the plasticized polymer electrolyte system mayimprove characteristics related to the interfaces that are formedbetween the electrolyte and its neighboring layers. As with the firstclass of polymer electrolytes, the plasticized polymer electrolytesystem may be laminated under high temperature conditions to improveadherence to the electrodes.

In an example, a plasticizer for use with poly (vinylidenefluoride)(PVDF) polymer or poly(vinylidene fluoride-hexafluoropropylene)(PVDF-HFP) copolymer electrode member compositions is propylenecarbonate (PC). The effective proportion of this plasticizer, may dependnot only on characteristics of a desired matrix polymer itself. Theeffective proportion may also be heavily influenced by the amounts andproperties of other components of the composition, such as the volumeand particle size of the active electrode material. For example, aneffective amount of PC in a positive electrode formulation with PVDF-HFPmay vary from about 60 percent to 300 percent by weight of the electrodematrix polymer component. Thus, in view of the numerous compositionvariables that are adjustable, the amount of plasticizer in anyformulation may be determined empirically in the rather broad range ofeffective amounts and may depend upon use conditions or on testedelectrical results.

In another exemplary class of electrolyte systems, gel electrolytesystems may be another type of electrolyte system used in polymerelectrolyte batteries. A gel is a type of polymerization product thathas different properties than a solidified polymer network. Gels consistof a solid three-dimensional network. The network typically may beformed by a copolymerization of branched monomers. The three dimensionalnetwork spans a volume of a liquid and binds it in place through surfacetension effects. There may be numerous polymer systems that may form agel electrolyte system such as PMMA, polyacrylonitrile (PAN), poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and numerous otherexamples. The gel electrolytes may typically exhibit high ionicconductivity. High temperature lamination may be used to affix the gelpolymer electrolyte to electrode surfaces with good adhesioncharacteristics. After the high temperature lamination processing, anelectrolyte composition may be added to the attached gel polymerbackground much as a sponge absorbs a liquid composition.

The various classes of polymer electrolyte layers may be used inexamples of polymer electrolyte batteries. Given a system including atype of anode material, ions consistent with transport of the anodematerial away from the anode may be included in the electrolyte as it isformed or in some examples, such as with the gel polymer electrolytesystem, added later. The polymer network of each of the classes createsa layer that may act as a separator for the batteries as well.

In an example, a polymer electrolyte/separator film may be prepared bycasting a portion of a coating composition onto a polished silicon waferusing a common spin-coating apparatus operated at a desired speed, suchas 600 rpm, for a desired time, such as for 2 sec, to obtain a film of adesired thickness and uniformity. The film may be dried at roomtemperature for an appropriate time, such as for about 10 minutes withinthe confines of the coating apparatus. The coating composition may beprepared by suspending about 1.5 g of an 88:12 VDF:HFP copolymer ofabout 380×103 MW Kynar FLEX 2801 in about 9 g of anhydroustetrohydrofuran (THF) and adding to this mixture about 1.5 g of a 1Msolution of zinc acetate, or other appropriate electrolyte salts, in a1:1 mixture by weight of ethylene carbonate (EC):propylene carbonate(PC). The completed mixture may be warmed to an elevated temperature,such as about 60 degrees C. for a period of time, such as 30 minutes, tofacilitate dissolution. Occasional agitation of the solution may help tomaintain the solution's fluidity. The resulting film may be used as apolymer electrolyte film according to the various examples to formbattery cells presented in this discussion.

It may be useful in some examples to create a porous membrane that ismade from a polymer backbone which is then impregnated with electrolyte.In a non-limiting example, a casting solution may be formed by mixing aroughly two-to-one ratio of poly(vinylidene fluoride) (PVDF) andpoly(dimethylsiloxane) (PDMS) into a solvent mixture comprising N—NDimethyl Acetamide (DMAc) and glycerol. The ratio of the DMAc toglycerol may be varied and may affect characteristics such as theporosity of the resulting separator layer. An excess of the solventmixture may be used to allow for the shrinkage of the resulting layer inthe cavity to form a thin separator layer. The resulting solution may becast upon an electrolyte, rolled into a sheet, or extruded into a shapein some examples. Other manners of dispensing the casting solution maybe consistent with the processes described herein. Thereafter, thestructure may be immersed into a room temperature water bath for 20-40hours to allow for the glycerol to dissolve out of the separator layerand result in a layer with a desired porosity. The polymer electrolytelayer may then be impregnated with a solution containing an appropriatesolvent such as water and an electrolyte such as a zinc based salt.

Another means of producing a battery cell containing a polymerelectrolyte with pores for incorporated electrolyte may be to start witha gel polymer such as a PVDF based system described above. Electrodesmay be laminated to the polymer electrolyte with a heated double-rolllaminator device at about 110 degrees C. and about 10 kg/cm rollpressure. After cooling, the laminate cell structure may be immersed inan appropriate solvent to extract electrode related plasticizer. In someexamples, the solvent may include acetone, diethyl ether or NMP. Theresulting structure may then be air dried until the surface solventevaporates and thereafter may be placed in a circulating air oven atelevated temperature such as about 70 degrees C. for an hour or so tocontinue the removal of solvent, moisture and residual plasticizer. Theprocessing may result in a well bonded work piece which may then bepackaged in an hermetically sealed multilayer foil/polymer envelope in ahelium atmosphere along with a measure of electrolyte such as a zincsalt dissolved in an appropriate solvent. The solvent and electrolytemay diffuse into the microporous membrane and impregnate it withelectrically conductive electrolyte.

Another means of producing a battery cell containing a polymerelectrolyte with pores for incorporated electrolyte may be to start witha commercial available microporous separator membrane. A laminatedelectrochemical battery cell may be prepared by assembling theelectrodes including the cathode and the anode respectively along with aCelgard 2300 microporous separator which may contain the electrolyte.The electrodes may be laminated to the separator with a heateddouble-roll laminator device at about 110 degrees C. and about 10 kg/cmroll pressure.

Exemplary Illustrated Processing of Energization Element—PolymerElectrolyte

Referring to FIGS. 4A-4F, a demonstration of processing of a polymerelectrolyte battery comprising a type of polymer electrolyte may befound. The various layers to be formed may be processed in variousfashions and orders, but as an example, a process may start at FIG. 4Awith obtaining a cathode collector 410. In an example, a thin foil orfilm of zinc metal may be used for the cathode collector. To aid inadhesion of the cathode layer, a surface treatment may be made to add acoating 415 to a surface of the titanium foil. In a non-limiting examplethe treatment may be a carbon coating such as offered by LamartCorporation, Clifton, N.J., USA. In some examples a region of thetitanium foil may be left untreated to form a cathode contact 416. Inother examples, the entire foil may be treated to add a coating, and thecoating may be removed in a later step to expose the cathode contact416.

Next at FIG. 4B, a cathode mixture may be added upon the coating to forma cathode 420. There may be numerous means to add the coating includingspraying, printing, and depositing with a squeegee or knife edge typelayering process. In the knife edge layering, an amount of the cathodemixture may be deposited behind a knife edge while the knife edge isdrawn along the cathode layer to result in a controlled layer withuniform thickness. In some other examples, a cathode may be formed byelectrodepositing the cathode material upon a current conductor.

One example of a completed cathode mixture formulation may be formed asfollows. A cathode powder blend composed of 88 percent Erachem MnO₂powder, jet-milled by Hosikowa, may be combined with Super P Li carbonblack, to a 5 percent composition and with Kynar 2801 PVDF to a 7percent composition. An amount of zinc acetate may be dissolved in NMPsuch that when mixed with the cathode powder blend, the amount of zincacetate is in a ratio of 1:10 for the zinc acetate mass to PVDF mass.When mixed the resulting slurry may be suspended in the NMP and thisamount of NMP creates a formulation with 27 percent solids.

The resulting slurry may be mixed with a magnetic stir bar for 10 to 20hours at a rate such as at roughly 400 rpm. The mixed slurry may bedegassed. Degassing may be processed with a Thinky ARE-250 planetarycentrifugal mixer at 2000 rpm for about 2 minutes.

The slurry may next be applied with a doctor blade to a thickness ofabout 30-80 microns. The slurry deposit may be made upon a sheet of 12.5micron thick grade I titanium foil such as that available from ArnoldMagnetics, which may be coated with a 1-3 micron thick layer of carbon.The cathode coating on the titanium foil may be dried in a heatedlaboratory oven for numerous hours, such as for a period of 18-24 hourswhere the temperature may in an example, be 50 degrees C.

Further enablement for the formulations and processing of cathodemixtures in biomedical devices may be found as set forth in U.S. patentapplication Ser. No. 14/746,204 filed Jun. 22, 2015, which isincorporated herein by reference.

Next, at FIG. 4C the polymer electrolyte 430 may be added to the growingstructure. As mentioned there may be numerous types and classes ofpolymer electrolytes that may be applied. In an example, the gel polymermay be composed of Kynar 2801 with 30 weight percent zinc acetate. Thismixture may be carried in a solvent blend including 36 percent DMSO and64 percent NMP. This solution may then be applied to the cathode using adoctor blade. The resulting coating may be dried in a high temperatureenvironment. In an example, the drying may be performed at around 50degrees C. in laboratory oven for a number of hours, such as 3-6 hours.In some examples, a further drying step at an even higher temperaturesuch as 100 C may be performed for some time, such as for 1 hour. Thiscoating process may be repeated multiple times to achieve a targetedthickness.

There may be numerous manners to apply the polymer electrolyte layersuch as by spray coating, printing, or squeegee or knife edge layeringHere again, the deposited layer may be dried to remove an amount of thesolvent.

Referring to FIG. 4D, a zinc anode 440 may be applied to the polymerelectrolyte layer. Further enablement for the formulations andprocessing of anodes in biomedical devices may be found as set forth inU.S. patent application Ser. No. 14/819,634 filed Aug. 6, 2015, which isincorporated herein by reference.

In some examples the surface layer of the polymer electrolyte may havean additional amount of solvent or polymer electrolyte reapplied to aidin bonding between the polymer electrolyte and the anode layer. In otherexamples, the bonding process may proceed with no solvent or polymerelectrolyte reapplication. There may be numerous manners to apply thezinc anode; however, in an example, a foil of zinc may be laminated tothe polymer electrolyte. In some examples, the lamination process willapply heat and pressure while evacuating the gas phase around the regionbeing applied. Lamination of electrodes with coated polymer electrolytesmay be carried out between heated pressure rollers at a temperature andpressure level which does not significantly affect the polymerstructure. For example, lamination may be carried out between 70 degreesC. and 130 degrees C., preferably between 100 degrees C. and 125 degreesC., and more preferably at about 110° C. The pressure, in some examples,may be a linear pressure load between about 20 and 180 kilograms percentimeter (kg/cm), preferably between about 55 and 125 kg/cm. It may beapparent that the optimum temperature and pressure conditions willdepend on the particular laminator construction and mode of its use.

In some examples, rolls of material may be processed in the mannersdescribed in FIGS. 4A-4C and then come together in the hot vacuumlamination process related to FIG. 4D. This processing may be referredto as a roll to roll manufacturing process.

Referring to FIG. 4E, the resulting polymer electrolyte battery devicemay be annealed in a thermal treatment 450 that will dry the structure.In some examples, the thermal treatment may also improve characteristicsat the newly formed interfaces between the collectors, cathode,electrolyte and anode.

The function of the formed battery as well as its biocompatibility maydepend strongly on encapsulating the polymer electrolyte batterystructure in manners that isolate the battery structure from itsenvironment while allowing battery contacts to be made to devicesoutside the encapsulation. The various means of encapsulation as havebeen discussed in sections on sealing and packaging heretofore may beused to perform the encapsulating step 460 illustrated in FIG. 4F.

Further enablement for the formulations and processing of anodes inbiomedical devices may be found as set forth in U.S. patent applicationSer. No. 14/827,613 filed Aug. 17, 2015, which is incorporated herein byreference.

In some examples, a pair of encapsulating films may be used to surroundthe battery element. The films may be precut in various locations toexpose the regions where collector contacts are located. Thereafter, thetwo films may be brought around the battery element and joined togetheris a seal. In some examples, the seal may be formed by thermallytreating the sealing layers to flow into each other and form a seal. Inother related examples, a laser may be used to form a seal. There may beother sealing materials, such as glues and adhesives that may be addedupon the formed seal to improve the seal integrity.

There may be other post processing that is performed upon the batteryelements. In examples where rolls of material are treated to form theencapsulated battery elements, a subsequent process may singulate or cutout the battery elements from the resulting sheet that is formed. Alaser may be used to cut out the batteries. In other examples a die maybe used to punch out the battery elements with a specifically shapedcutting surface. As mentioned previously, some singulated batterydesigns may be rectilinear whereas other designs may be curvilinear,matching a curve of a contact lens insert piece for example.

Exemplary Performance Results for Polymer Electrolyte Batteries.

Exemplary samples of polymer electrolyte batteries have been formedutilizing the processing example referred to in relation to FIGS. 4A-4F.Referring to FIG. 5A-D, characterization results from the exemplarysamples are found. Samples were formed with an overall form factor of 5mm by 1 mm and a thickness of approximately 135 microns. Forcharacterization data, the effective anode area for the battery sampleswas roughly 3×10⁻³ cm². At FIG. 5A, the discharge characteristics of anexemplary battery cell may be found. A steady performance with a cellvoltage of approximately 1.3V may be observed indicating good energycapacity and cell life performance. At FIG. 5B, frequencycharacterization of exemplary samples have been performed and aresulting “Nyquist” plot is displayed. At FIGS. 5C and 5D the rawfrequency characters are displayed. FIG. 5C displays the impedanceversus frequency results obtained. FIG. 5D displays the phase angleversus frequency results measured from exemplary samples.

Well-designed sealing structures and the associated sealing materialsmay improve biocompatibility of the energization device as materials maybe maintained in zones that have no interaction with biologicallycontacting surfaces. In addition, well-formed seals may improve theability of the battery to receive forces of various kinds and notrupture exposing the contents of the cavity or cavities of a battery.

The polymer electrolyte composition inherently improves biocompatibilityof the energization element as well as its resiliency to effect fromexternal diffusion into the battery. The solid-state aspect of thepolymer backbone and its containment of ions whether in solvent or notminimizes forces that may cause loss of electrolyte by diffusion out ofthe device.

The examples herein have discussed polymer electrolyte primary batterydevices which have been formed according to the various mannersdescribed in the present invention. At a higher level, in some examples,these battery devices may be incorporated into biomedical devices suchas ophthalmic lenses as discussed in reference to FIG. 1B.

In the examples of contact lenses, the battery device may be connectedto an electroactive element where the battery resides within an insertwith the electroactive element or outside the insert. The insert, theelectroactive element and the battery as a whole may be encapsulatedwith appropriate hydrogel formulations to afford biocompatibility of thebiomedical device. In some examples, the hydrogel may containformulations that retain the wetting aspects of the encapsulatinghydrogel. Thus, numerous aspects of biocompatibility related to theshell that contains components are relevant to the biocompatibility ofthe biomedical device as a whole. These aspects may include oxygenpermeability, wettability, chemical compatibility, and solutepermeability as a few non-limiting examples.

The battery and the insert may interact with wet environments, andtherefore the strategies for biocompatibility of the battery alone arevery relevant to the overall biomedical device. In some examples it maybe envisioned that seals prevent ingress and egress of materials intothe insert and into the battery device. In these examples, the design ofthe hydrogel encapsulating layer may be altered to allow wettability andpermeability around the insert and the battery device, for example. Insome other examples, gas evolution may allow some gas species to passthrough battery devices, through hydrogel encapsulation and into thebiomedical device environment. The portions of a biomedical device,whether for an ophthalmic device or for other devices, that contactfluids and cell layers of a user may be designed for matching of theinterface layers of the biomedical device to the biologic environmentthat the biomedical device will reside in or on.

External Encapsulating Layers of Electroactive Devices and Batteries

In some examples, a preferred encapsulating material that may form anencapsulating layer in a biomedical device may include a siliconecontaining component. In an example, this encapsulating layer may form alens skirt of a contact lens. A “silicone-containing component” is onethat contains at least one [—Si—O—] unit in a monomer, macromer orprepolymer. Preferably, the total Si and attached O are present in thesilicone-containing component in an amount greater than about 20 weightpercent, and more preferably greater than 30 weight percent of the totalmolecular weight of the silicone-containing component. Usefulsilicone-containing components preferably comprise polymerizablefunctional groups such as acrylate, methacrylate, acrylamide,methacrylamide, vinyl, N-vinyl lactam, N-vinylamide, and styrylfunctional groups.

In some examples, the ophthalmic lens skirt, also called aninsert-encapsulating layer, that surrounds the insert may be comprisedof standard hydrogel ophthalmic lens formulations. Exemplary materialswith characteristics that may provide an acceptable match to numerousinsert materials may include, the Narafilcon family (includingNarafilcon A and Narafilcon B), and the Etafilcon family (includingEtafilcon A). A more technically inclusive discussion follows on thenature of materials consistent with the art herein. One ordinarilyskilled in the art may recognize that other material other than thosediscussed may also form an acceptable enclosure or partial enclosure ofthe sealed and encapsulated inserts and should be considered consistentand included within the scope of the claims.

Suitable silicone containing components include compounds of Formula I

where

R1 is independently selected from monovalent reactive groups, monovalentalkyl groups, or monovalent aryl groups, any of the foregoing which mayfurther comprise functionality selected from hydroxy, amino, oxa,carboxy, alkyl carboxy, alkoxy, amido, carbamate, carbonate, halogen orcombinations thereof; and monovalent siloxane chains comprising 1-100Si—O repeat units which may further comprise functionality selected fromalkyl, hydroxy, amino, oxa, carboxy, alkyl carboxy, alkoxy, amido,carbamate, halogen or combinations thereof;

where b=0 to 500, where it is understood that when b is other than 0, bis a distribution having a mode equal to a stated value;

wherein at least one R1 comprises a monovalent reactive group, and insome examples between one and 3 R1 comprise monovalent reactive groups.

As used herein “monovalent reactive groups” are groups that may undergofree radical and/or cationic polymerization. Non-limiting examples offree radical reactive groups include (meth)acrylates, styryls, vinyls,vinyl ethers, C1-6alkyl(meth)acrylates, (meth)acrylamides,C1-6alkyl(meth)acrylamides, N-vinyllactams, N-vinylamides, C2-5alkenyls,C2-5 alkenylphenyls, C2-5 alkenylnaphthyls, C2-6alkenylphenylC1-6alkyls,O-vinylcarbamates and O-vinylcarbonates. Non-limiting examples ofcationic reactive groups include vinyl ethers or epoxide groups andmixtures thereof. In one embodiment the free radical reactive groupscomprises (meth)acrylate, acryloxy, (meth)acrylamide, and mixturesthereof.

Suitable monovalent alkyl and aryl groups include unsubstitutedmonovalent C1 to C16alkyl groups, C6-C14 aryl groups, such assubstituted and unsubstituted methyl, ethyl, propyl, butyl,2-hydroxypropyl, propoxypropyl, polyethyleneoxypropyl, combinationsthereof and the like.

In one example, b is zero, one R1 is a monovalent reactive group, and atleast 3 R1 are selected from monovalent alkyl groups having one to 16carbon atoms, and in another example from monovalent alkyl groups havingone to 6 carbon atoms. Non-limiting examples of silicone components ofthis embodiment include2-methyl-,2-hydroxy-3-[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propoxy]propylester (“SiGMA”),

2-hydroxy-3-methacryloxypropyloxypropyl-tris (trimethylsiloxy)silane,

3-methacryloxypropyltris(trimethylsiloxy)silane (“TRIS”),

3-methacryloxypropylbis(trimethylsiloxy)methylsilane and

3-methacryloxypropylpentamethyl disiloxane.

In another example, b is 2 to 20, 3 to 15 or in some examples 3 to 10;at least one terminal R1 comprises a monovalent reactive group and theremaining R1 are selected from monovalent alkyl groups having 1 to 16carbon atoms, and in another embodiment from monovalent alkyl groupshaving 1 to 6 carbon atoms. In yet another embodiment, b is 3 to 15, oneterminal R1 comprises a monovalent reactive group, the other terminal R1comprises a monovalent alkyl group having 1 to 6 carbon atoms and theremaining R1 comprise monovalent alkyl group having 1 to 3 carbon atoms.Non-limiting examples of silicone components of this embodiment include(mono-(2-hydroxy-3-methacryloxypropyl)-propyl ether terminatedpolydimethylsiloxane (400-1000 MW)) (“OH-mPDMS”), monomethacryloxypropylterminated mono-n-butyl terminated polydimethylsiloxanes (800-1000 MW),(“mPDMS”).

In another example, b is 5 to 400 or from 10 to 300, both terminal R1comprise monovalent reactive groups and the remaining R1 areindependently selected from monovalent alkyl groups having 1 to 18carbon atoms, which may have ether linkages between carbon atoms and mayfurther comprise halogen.

In one example, where a silicone hydrogel lens is desired, the lens ofthe present invention will be made from a reactive mixture comprising atleast about 20 and preferably between about 20 and 70% wt siliconecontaining components based on total weight of reactive monomercomponents from which the polymer is made.

In another embodiment, one to four R1 comprises a vinyl carbonate orcarbamate of the formula:

wherein: Y denotes O—, S— or NH—;

R denotes, hydrogen or methyl; d is 1, 2, 3 or 4; and q is 0 or 1.

The silicone-containing vinyl carbonate or vinyl carbamate monomersspecifically include:1,3-bis[4-(vinyloxycarbonyloxy)but-1-yl]tetramethyl-disiloxane;3-(vinyloxycarbonylthio) propyl-[tris (trimethylsiloxy)silane];3-[tris(trimethylsiloxy)silyl]propyl allyl carbamate;3-[tris(trimethylsiloxy)silyl]propyl vinyl carbamate;trimethylsilylethyl vinyl carbonate; trimethylsilylmethyl vinylcarbonate, and

Where biomedical devices with modulus below about 200 are desired, onlyone R1 shall comprise a monovalent reactive group and no more than twoof the remaining R1 groups will comprise monovalent siloxane groups.

Another class of silicone-containing components includes polyurethanemacromers of the following formulae:(*D*A*D*G)a*D*D*E1;E(*D*G*D*A)a*D*G*D*E1 or;E(*D*A*D*G)a*D*A*D*E1  Formulae IV-VI

wherein:

D denotes an alkyl diradical, an alkyl cycloalkyl diradical, acycloalkyl diradical, an aryl diradical or an alkylaryl diradical having6 to 30 carbon atoms,

G denotes an alkyl diradical, a cycloalkyl diradical, an alkylcycloalkyl diradical, an aryl diradical or an alkylaryl diradical having1 to 40 carbon atoms and which may contain ether, thio or amine linkagesin the main chain;

* denotes a urethane or ureido linkage;

a is at least 1;

A denotes a divalent polymeric radical of formula:

R11 independently denotes an alkyl or fluoro-substituted alkyl grouphaving 1 to 10 carbon atoms, which may contain ether linkages betweencarbon atoms; y is at least 1; and p provides a moiety weight of 400 to10,000; each of E and E1 independently denotes a polymerizableunsaturated organic radical represented by formula:

wherein: R5 is hydrogen or methyl; R13 is hydrogen, an alkyl radicalhaving 1 to 6 carbon atoms, or a —CO—Y—R15 radical wherein Y is —O—,Y—S— or —NH—; R14 is a divalent radical having 1 to 5 carbon atoms; Xdenotes —CO— or —OCO—; Z denotes —O— or —NH—; Ar denotes an aromaticradical having 6 to 30 carbon atoms; w is 0 to 6; x is 0 or 1; y is 0 or1; and z is 0 or 1.

A preferred silicone-containing component is a polyurethane macromerrepresented by the following formula:

wherein R16 is a diradical of a diisocyanate after removal of theisocyanate group, such as the diradical of isophorone diisocyanate.Another suitable silicone containing macromer is compound of formula X(in which x+y is a number in the range of 10 to 30) formed by thereaction of fluoroether, hydroxy-terminated polydimethylsiloxane,isophorone diisocyanate and isocyanatoethylmethacrylate.

Other silicone containing components suitable for use in this inventioninclude macromers containing polysiloxane, polyalkylene ether,diisocyanate, polyfluorinated hydrocarbon, polyfluorinated ether andpolysaccharide groups; polysiloxanes with a polar fluorinated graft orside group having a hydrogen atom attached to a terminaldifluoro-substituted carbon atom; hydrophilic siloxanyl methacrylatescontaining ether and siloxanyl linkanges and crosslinkable monomerscontaining polyether and polysiloxanyl groups. In some examples, thepolymer backbone may have zwitterions incorporated into it. Thesezwitterions may exhibit charges of both polarity along the polymer chainwhen the material is in the presence of a solvent. The presence of thezwitterions may improve wettability of the polymerized material. In someexamples, any of the foregoing polysiloxanes may also be used as anencapsulating layer in the present invention.

Biomedical Devices Using Polymer Electrolyte Batteries

The biocompatible batteries may be used in biocompatible devices suchas, for example, implantable electronic devices, such as pacemakers andmicro-energy harvesters, electronic pills for monitoring and/or testinga biological function, surgical devices with active components,ophthalmic devices, microsized pumps, defibrillators, stents, and thelike.

Specific examples have been described to illustrate sample embodimentsfor the cathode mixture for use in biocompatible batteries. Theseexamples are for said illustration and are not intended to limit thescope of the claims in any manner. Accordingly, the description isintended to embrace all examples that may be apparent to those skilledin the art.

Although shown and described is what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

What is claimed is:
 1. A biomedical device comprising: an electroactivecomponent; a primary battery including an anode current collector, acathode current collector, an anode, a dry polymer electrolytecomprising an ionic species, and a transition metal oxide cathode,wherein the dry polymer electrolyte is laminated to a transition metaloxide deposit and to the anode; and a first biocompatible encapsulatinglayer, wherein the first biocompatible encapsulating layer encapsulatesat least the dry polymer electrolyte, the metal oxide deposit, and thecathode current collector.
 2. The biomedical device of claim 1, whereinthe anode comprises zinc, wherein the anode and the anode currentcollector are a single layer, and wherein the transition metal oxidecathode comprises manganese.
 3. The biomedical device of claim 2,wherein the composition of the electrolyte comprises poly (vinylidenefluoride).
 4. The biomedical device of claim 3, wherein the compositionof the electrolyte comprises zinc ion.
 5. The biomedical device of claim4, wherein the composition of the manganese dioxide cathode comprisesjet milled electrolytic manganese dioxide.
 6. The biomedical device ofclaim 4, wherein the composition of the manganese dioxide cathodecomprises poly(vinylidine fluoride).
 7. The biomedical device of claim6, wherein the composition of the manganese dioxide cathode comprisescarbon black.
 8. The biomedical device of claim 7, wherein the zincanode is a foil of zinc.
 9. The biomedical device of claim 1, whereinthe battery comprises a seal in encapsulating films that enclose thebattery portions not used for making external contacts.
 10. Thebiomedical device of claim 1, wherein the thickness of the battery isless than 1 mm at least along a first dimension of the extents of thebattery.
 11. The biomedical device of claim 1, wherein the thickness ofthe battery is less than 500 microns at least along a first dimension ofthe extents of the battery.
 12. The biomedical device of claim 1,wherein the thickness of the battery is less than 250 microns at leastalong a first dimension of the extents of the battery.
 13. Thebiomedical device of claim 12, wherein the shape of the battery iscurvilinear.